1. Field of Invention
The present invention relates to a valve for operation in freezing conditions and in particular for a butterfly valve which can have a heated capability for handling cold fluids or product from which moisture emanates under vacuum conditions, i.e. sublimation, and a method for modification of existing butterfly valves so as to provide heated capability.
2. Description of the Prior Art
It is known in the art to provide fluid control valves comprising a valve body structure having a fluid flow passage therethrough and a first sealing surface means and a closure structure for controlling fluid flow through the passage with the closure structure having a second sealing surface means adapted to engage the first sealing surface means to shut off fluid flow through the associated valve.
In many situations, fluid control valves are often used to control the flow of fluids wherein the fluid is at a particular temperature which tends to disrupt or interfere with the normal operation and sealing of the valve. This disruption or interference oftentimes occurs when the fluids passing therethrough are of an extremely low temperature. It also occurs in instances where moisture containing product gives off the moisture under vacuum conditions resulting in sublimation preventing its normal operation such that the valve cannot be closed complete so as to shut off or cease the fluid flow therethrough.
This problem has been addressed in that there are designs for valves which will prevent a sublimation and the concomitant disruption or interference of the valve operation. However, such valves are more expensive by a factor of 10 over a normal valve.
There is therefore a need for a relatively inexpensive valve which is not subject to sublimation and a need for a manner of modification of existing valves to provide for a heating element so as to prevent sublimation. Applicant's invention addresses both of these problems.